Babaud



Sept. 2, 1952 J. BABAUD 2,609,410

MOVABLE MAGNET OSCILLOGRAPH Filed Oct. 11, 1949 Jan 54 baud PatentedSept. 2 1952 :MOVABLELMAGNET 'osci' ttoc tsrn that examine, i aris, 1France, "to Etablissements Charles B-eairdoiiim- Paris,

Application gotte -{11, 1949, S er ial 420,725

QInf. FrancelOctober 15, 1948 i 6;. "This invention relates {toosiliograph of the movable magnet tyiiai'andits object is to vide a"movable magnet "oscillog'raphpf new an improved construction, of'greatlyireduced "buik a's cbmpa'red with' conventional apparatus ofsimilar typejwhile at the same time possessing increasedaccuracyi'andcapablebf retaining over very long periods f time "itsdesir'aibie "characteristics "of sensibilityan'd precision.

' For-"man ye'ars' inthe tonstruction-or certain hysteresis-into; thecircuitffinal'ly,'itis difficult tosecure uniform damping regardless ofthe'tem perature. At the present timehoweverfirriet'al alloys'areknownhaving suitable magnetic characteristics for the constructionof magnetic vane elements and iron circuits'a'nii moreover it has been'rouriu that certam substances aregadap ted to Provide a highlysuccessful damping' mdiumc Thus, it-is-an object of this invention toprovide a movable magnet oscillograph of such construction"'a'stoconstitute an instrument whichyvi'l'lnot break "easily; which ishandy to*operateand :p'ossesses'fve'ryreduced dimensions'and compr es-a suitablesus ending and damping arrangement fora magnetic'vaneelement.

It is another object of the invention to provide an oscillograph of thetype described which, on account of the peculiar relative arrangement,to be described, between the magnetic vane element and the fieldelements thereof, as well as the use of special materials, to bespecified, for the construction of the fixed armature and the dampingmedium, will possess a very high sensitivity and a desirably highfidelity.

According to the invention, an improved oscillograph comprises a bodyterminating in an armature of reduced diameter serving as a centeringmeans for a circular coil winding which provides the field-generatingmeans, and adapted to receive over the end thereof a carrier means for amovable structure formed with a central optic'al "aperture, said"carrier, in cooperation a. disc member of resilient material-placed b"a it and separatin it'irom theheidmea name a e'aieu enclosurefore-harsher in" the movable magnetic structure ist'suspendeufiirdwiiichis fih u withscanning-hum.

"The rnetal'rrcm The damping medium "comprises 'atransp enft liquid the'visctsity offwhi'c does 'fot vary'sreatiy with tempersture'suchas e?The 'use "of the .specified'mate possible'fto construct langapparatus wicn w lie having desirable sens tiv tyarrurretu" 'l'f' eney tocharacteristics, win he ,or greatly uu ed tux :eorrrpareaitox'whet "it"wasgptssibie' r eor strieteu byiimit topswinpr al r sitive'andquic'k-"operating p'o1arized""gna1meahs The above-described andfurther fobiet matures of theintentioniwiii appear" rof'm the nsuingdescription or heernbouim'nt o vention, selected torpur oses'of musvatib not oriiimitation, fwitnfrererence toth'e'.

arse-tube io i rue-eta 'Eiguel Li's .alons i paratu 7 g 'Fig're is acrosseseetion ion" l'i'n'e'iII v Figured. 3 v

JA's shown the j'drawifngs, the eary: instrument is "formed towardsitsrear-"en ward the left as shown in Figure 1) and for the purpose ofmounting it on a support not shown, with a transversely extending notch2 with which a presser spring 3 and a set screw 4 are associated.

Toward the front or right-hand end (as in Fig. 1) the body I is formedwith a cylindrical part 5 extended by a core section 6 of reduceddiameter, over which an annular coil 1 is seated, the wires 8 of saidcoil being adapted for connection with a circuit on which measurementsare to be ef fected.

The structure including the cylindrical part 5 and the winding 1 iscovered by a sleeve 9 terminating flush with the end or" the core andexternally formed with a screw-thread III. This V. V 3 screw-thread isadapted to receive thereover the rear portion of a bushing ll providedwith an inwardly-directed flange [2 at it front end, said flange beingadapted to engage the outer face of a magnet-carrier l3 inserted in saidbushing to clamp said carrier against a sealing gasket or disc I4 madeof a resilient material, seated against the coreand against the end of.the sleeve.

The magnet-carrier I3 is formed with a hole extending from its front andaxially of the core and opening into a recess containing an opticalsystem l5 comprising for example a simple lens sealingly secured withinsaid recess. The rear part of the magnet-carrier I3 is bored to define acylindrical chamber [6 sealed rearwardly with the sealing disc (4.

The mirror-carrying vane-shaped magnet member I! is made of metal havinga high coercive force such as an aluminium-nickel-cobalt, aplatinum-cobalt, or a silicon-manganese-alualloy, or certain suitablesintered oxidesi V It is secured at the center of a torsion strip 18anchored and soldered at both ends in oppositely-located holes formed ina copper ring I9.

The ring (Fig. 2) is formed with an opening or slot 20 in the vicinityof one of said holes and is weakened in certain sections thereof bybeing externally milled. The segment 28 tapers down towards its free endadjacent the slot and the strip is soldered after first having placedsaid segment under tension by imparting a slight camber thereto. Theother segment is weak ened throughout its extent except at a number ofcontact bosses 22, so as to concentrate on said segment any bendingstrains occurring upon the ring being forced into the bore. In this way,the segment 2i will continue to supply the requisite tension since itdoes not undergo any distorsion as the ring is inserted into the bore.The'sealed chamber I6 is filled with a suitable damping fluid, such assilicone oil. The chamber capacity is restricted by the disc 1% and onlycontains a very small quantity of damping liquid and, owing to thepresence of said resilient disc, it may be completely filled, as theresilient disc will allow for any variations in volume of the liquid dueto expansion. I .The use of special allows such as thealuminium-nickel-cobalt alloy known as Alnico, for the construction ofthe magnetic vane, and the useof suitably heat-treated ferro- -nickelfor the armature, and of silicone oil as a damping medium, make itpossible to obtainhigh accuracy and excellent sensitivity in theapparatus. Thus witha .400 ohm winding, anatural frequency of 180 cyclesand a fidelity index of 1%, mirror-displacements of about 190millimeters per milliampere have been obtained at a distance of onemeter.

It will of course be understood that the invention is not restricted tothe specific embodiment illustrated and described, given by way ofexample only. Thus, a similar arrangement could be adopted inconstructing a polarized signal means, in which the magnet vane iseither suspended to a strip, as in the example shown, or supported on aspring-plate or the like, and its movements restricted by two stops.

What I claim is:

l. A movable magnet oscillograph comprising in combination a body ofmagnetic material forming the armature of an electromagnet with acentral core extension, an electrical winding on said core, a sleevesecured to said body around said core, a sealing gasket of non magneticmaterial against the end of said sleeve and core, a hollow cover againstsaid gasket having a centrally apertured end fitted with a lens anddefining a closed chamber in front of said gasket, means tightlyclamping said cover with the interposed gasket against said body, anannular fitting of non magnetic material inserted in said chamber andformed with an arcuate peripheral arm, a torsion strip attached undertension between said arm and the diametrically opposed point of saidfitting, a mirror carrying vaneshaped magnet mounted on said torsionstrip, and a, damping liquid filling said chamber.

2. A movable magnet oscillograph according to claim 1, in which incombination the said armature of the electromagnet is of a magneticmaterial of low hysteresis, such as ferro-nickel, the said vane-shapedmagnet is of an alloy having a high coercive force such as analuminumnickel-cobalt alloy and the said clamping liquid is a liquid theviscosity of which varies but little with temperature, such as siliconeoil.

3. A movable magnet oscillograph according to claim 1, wherein the saidchamber is cylindrical and said fitting is a split ring, one half ofwhich is tapered in a circumferential direction toward the split, andthe other half of which comprises an arcuate segment having a weakenedsection throughout its length except for three outwardly directed bosseswhich center said ring in said cylindrical chamber- JEAN BABAUD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

